Protein kinases are a family of enzymes that participate in the signalling events which control the activation, growth and differentiation of cells in response to extracellular mediators and to changes in the environment. In general, these kinases fall into several groups; those which preferentially catalyse the phosphorylation of hydroxy groups of serine and/or threonine residues and those which preferentially catalyse the phosphorylation of hydroxy groups of tyrosine residues [S. K. Hanks and T. Hunter, FASEB. J., 1995, 9, pages 576-596]. Such phosphorylations may greatly modify the function of the proteins; thus, protein kinases play an important role in regulating a wide variety of cell processes including, especially, metabolism, cell proliferation, cell differentiation or cell survival.
Inappropriately high protein kinase activity has been implicated in many diseases resulting from abnormal cellular function. This might arise either directly or indirectly, for example by failure of the proper control mechanisms for the kinase, related for example to mutation, over-expression or inappropriate activation of the enzyme; or by over- or underproduction of cytokines or growth factors also participating in the transduction of signals upstream or downstream of the kinase. In all of these instances, selective inhibition of the action of the kinase might be expected to have a beneficial effect.
ITK, is a T cell specific tyrosine kinase of the Tec family that is required for normal Th2 function. Asthma is a disease characterised by increased Th2 cytokine production including IL-4. An inhibitor of ITK should therefore have an impact on disease progression in asthma through inhibition of Th2 cytokine production.
We have now found a novel group of thienopyrazoles, which have valuable pharmaceutical properties, in particular, the ability to inhibit protein kinases, more particularly, the ability to inhibit the protein kinase ITK.